"A bromance can be a good thing," said the study's lead author Elizabeth Kirby, who you can quote next time your significant other glares at you for staying out with the boys too late.

Her research centred on the hormone oxytocin, which has previously been shown to help people bond and socialise more — which in turn helps them deal with stress, which in turn leads to longer and healthier lives.

Kirby's team measured the level of oxytocin in the brains of male rats housed in the same cage. After a "mild stress" where the rat bros were restrained for several hours, their oxytocin levels increased when they were reunited.

This made them more likely to share water "without pushing and shoving", behaviour Kirby described as "very civil" (basically the equivalent of splitting a pizza on a bromantic date).

The rats also "huddled and touched more", becoming more social than they had been in an unstressed environment — a response likened to humans coming together after national tragedies.

"Even rats can have a good cuddle – essentially a male-male bromance – to help recover from a bad day," said Kirby.

"These rats are using their rat friendships to recover from what would otherwise be a negative experience. If rats can do it, men can do it too."

She added that the research counters the assumption that "males are assumed to be instinctively aggressive" towards each other.

The study isn't just a good reminder to invite your best mate around for a barbecue. It may also have implications for the treatment of post-traumatic stress disorder (PTSD), which is already treated using oxytocin nasal sprays.

Interestingly, while mild stress increased oxytocin levels in the rats' brains, severe stress — exposing the restrained rats to the scent of fox urine, making them think they were about to be eaten —had the opposite effect.

"[The rats exposed to fox urine] don't have any of the prosocial bonding, they don't share resources in a nice way ... they don't huddle or bond, and you start seeing aggression," said the study's senior author, associate professor Daniela Kaufer.

This is akin to how PTSD can cause people to withdraw from their social networks after events such as a battle experience or a car accident, Kaufer said.